Usually when I think of energy harvesting, I think of flex sensors or capturing movement. Well, a team at MIT has figured out a way to capture even small movements according to a post by PCWorld. According to the team’s paper, “The device achieves long current pulse duration, which has not been achieved by other types of mechanical energy-harvesting devices.” In fact, their device achieved a generating capacity of 15%. Here’s the secret sauce:
Specifically, their technology uses two thin sheets of lithium alloys as electrodes, with a layer of porous polymer soaked with liquid electrolyte in between. When bent even just slightly, the layered composite produces a counteracting voltage and an electrical current in the external circuit between the two electrodes, which can be then used to power other devices.
They use the term “lithium migration” to describe the resulting current in the device when there is asymmetric stress creating the chemical difference. This is quite different from the two popular energy harvesting methods, triboelectric (think rubbing a balloon against wool), or piezoelectric (using crystals). MIT’s method is more cost effective.
Such traditional approaches have “high electrical impedance and bending rigidity, and can be quite expensive,” said Ju Li, Battelle Energy Alliance Professor in Nuclear Science and Engineering and professor of materials science and engineering at MIT.
Most harvesting methods are also meant for high frequency ranges, but this particular method works well for low frequency ranges like walking. So, this device is ideal for small movements in the arm and leg. Of course when you think of repetitive motion, you may worry about stress, but MIT’s device has held up well, keeping it’s integrity and performance even after 1,500 cycles. So, there is plenty of excitement about potential uses including “biomedical devices or embedded stress sensors in roads, bridges or even keyboards”. Although you may not have a lab at home fit for working on electrochemical devices, you can discover the power of movement and trigger your own reactions with an Arduino and one of our flex sensors. Try it in a glove or an elbow area of your sweatshirt and decide what event you would like to have happen. Could be nice for cosplay when you want to initiate a light sequence on a costume!
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